This Mentored Research Scientist Career Development Proposal is the first grant submitted by the candidate and follows approximately three years of postdoctoral training. Its main objective is to provide continued training to permit the candidate to make the transition to independence and launch a research career in the area of digestive diseases. The research will be done in the newly renovated, fully equipped modern research laboratory of the mentor, in a digestive diseases division renowned for excellence in clinical and basic research. Oxidative stress and signaling is rapidly emerging as a field of fundamental biological importance in areas as diverse as mitogenic signaling, inflammatory responses and apoptosis. The precise mechanisms involved, however, remain poorly understood. The candidate's proposed studies explore kinase cascades in cells undergoing oxidative stress and will focus in particular on the regulation of Protein kinase D, an enzyme recently cloned in the mentor's laboratory and exhibiting distinct structural, enzymological and regulatory properties. PKD has emerged as a putative downstream target of novel isoforms of PKC. Key findings described for the first time in this proposal indicate that PKD is potently activated during oxidative stress. The specific aims are to characterize oxidative stress-mediated PKD activation, including required upstream signals, and to measure and determine the role of reactive oxygen species in growth factor-mediated PKD activation. The candidate will draw upon prior experience in signal transducing second messengers and enzymes and gain new expertise to achieve these aims. The experimental approaches described will enable the candidate to become familiar with theoretical and practical aspects of signal transduction and oxidative stress in a variety of cell types including normal and cancer intestinal epithelial cells. Through close mentoring including frequent guidance and discussions of research, and active participation in seminars, conferences and national meetings, the candidate will progress to independence and then pursue his long-term goal of contributing to the understanding of gastrointestinal diseases through a research career in this area.